Switchable roller finger followers are known. See, for example, U.S. Pat. No. 7,174,869. Such finger followers have an outer lever pivotably mounted outside an inner lever and a roller rotatably mounted on a transverse axle in a slot in the inner lever. Here, the top surface of the outer lever can act as a contact surface for a high lift cam and the top surface of the roller acts as a contact surface for a low lift cam. A coupling element is mounted at one end of the finger follower and oil from an oil source is used to activate the coupling element. When the coupling element is activated, it locks the outer lever to the inner lever and requires the follower to follow the high lift cam and transfer the lift to the valve stem of an associated intake or exhaust valve. When the coupling element is deactivated, the outer lever is free to pivot relative to the inner lever, with the motion being absorbed by a lost-motion spring, and the motion of the low lift cam is transferred by the inner lever to the valve stem. This movement by the outer lever is conventionally referred to as the lost motion stroke.
Conventionally, the outer lever is a unitary structure such that the coupling element need only operate on one part of the outer lever. Typically, the coupling device operates on a yoke portion of the outer lever, the yoke portion being transverse to the longitudinal axis of the finger follower. Conventionally, the roller axle is staked to the inner lever to maintain its lateral position relative to the inner lever. U.S. Pat. No. 7,909,007 discloses a roller finger follower of this type. This provides a lost motion spring to maintain contact between the cam follower and the cam.
U.S. Pat. No. 8,251,032 discloses a prior switchable roller finger follower of one inventor in which two locking pins of the coupling device are extended outwardly to a locked position under each of outer arms via oil pressure, and are uncoupled via separate return springs when insufficient oil pressure is present. U.S. Pat. No. 8,251,032 is incorporated herein by reference as if fully set forth.
U.S. Pat. No. 8,726,862 and U.S. Pat. No. 8,752,513 disclose switchable finger followers with the coupling device formed by an actuatable locking pin having a flat that extends from the inner lever and engages under a stop surface on the outer lever. The locking pin is pre-assembled in the inner arm.
Switchable finger followers that provide for valve deactivation are also known in which the inner and outer levers are coupled together by a coupling element in the active state, and are uncoupled in the deactivated state, resulting in no lift being transferred to the valve stem.
One issue in these prior known adjusters is the lack of lash adjustment for the coupling element that connects the inner and outer levers in at least one operating state.
It would be desirable to provide a switchable finger follower of the general type noted above with simple manufacturing, as well as the possibility for adjusting the lash of the coupling element between the inner and outer levers.